WO1998025081A1

WO1998025081A1 - Cable drive assembly

Info

Publication number: WO1998025081A1
Application number: PCT/US1997/022288
Authority: WO
Inventors: Gregory A. Parkin; Ronald M. Gray
Original assignee: Copes-Vulcan, Inc.
Priority date: 1996-12-06
Filing date: 1997-12-05
Publication date: 1998-06-11
Also published as: AU5593598A

Abstract

A soot blower (10) incorporating an improved cable drive system. The soot blower (10) includes a housing (12), a travelling carriage (14) including a driven pulley (28) mounted in the housing (12) for reciprocal movement between an extended position and a retracted position, a drive cable (22), a forward tensioning assembly (32), a drive mechanism including a drive pulley (18), a rearward tensioning assembly (24), and a pair of front idler pulleys (34). The drive cable extends from a rear mounting member, around said driven pulley (28), around said drive pulley (18), around said front idler pulleys (34), and again around said driven pulley (28) to a front mounting member (36).

Description

CABLE DRIVE ASSEMBLY

BACKGROUND OF THE INVENTION

The present invention relates generally to soot blower assemblies and, more particularly, to travelling carriage cable drive assemblies for soot blowers. Soot blowers are used to inject a cleaning medium, such as steam, into boilers to remove soot and carbon deposits from interior surfaces of the boiler and boiler tubes. Conventionally, soot blowers include a lance that is secured to a travelling carriage. The traveling carriage moves toward and away from the boiler to insert and retract the lance tube. The lance tube, which has one or more nozzles at its outer end, is typically rotated as it is inserted and retracted to thereby spray cleaning medium on as much of the surrounding heat exchanger surfaces as possible. One of the challenges encountered by soot blowers is providing a travelling carriage drive mechanism which will perform reliably in the harsh operating environment surrounding commercial boilers. This challenge is compounded by the fact that diverse motion is required: traversing or longitudinal motion of the travelling carriage/ lance tube and rotary motion of the lance tube. One solution to these challenges has been to provide a cable drive system wherein a driven wheel of a travelling carriage is rotated by a drive wheel via a drive cable. Rotary motion of the driven wheel causes traversing motion along the drive cable and, via a transmission mechanism, rotary motion of the lance tube. Rotation of the drive wheel imparts motion to the driven wheel due to frictional engagement between the drive cable and the drive and driven wheels. Using a drive cable is thought to be preferred over other potential solutions, such as rack and pinion drive arrangements, due to its simplicity of design, reduction of moving parts, and ease of manufacture and assembly. One such cable drive system is taught by U.S. Patent No. 4,387,481, which is owned by the assignee of the present application and expressly incorporated herein in its entirety. In the '481 patent, a first drive cable has an end secured to a rotatable drum, and extends from the drum around a rearwardly mounted idler pulley, and forwardly to a rigid connection at the rear of the travelling carriage. A second drive cable has an end secured to the rotatable drum, and extends from the drum, around a large forwardly mounted idler pulley, and rearwardly to a rigid connection at the front of the traveling carriage. The first drive cable is used to pull the travelling carriage rearwardly, while the second drive cable is used to pull the travelling carriage forwardly. Although the cable drive system taught by the '481 patent works satisfactorily, it suffers from several disadvantages. Firstly, having a large front idler pulley increases the overall length of the soot blower, which is contrary to preferred design considerations. Secondly, having a pair of drive cables which are oppositely wound on a common drum is expensive from a manufacturing and labor standpoint. Thirdly, tensioning the drive cables may be problematic as they are independent of one another, and may require several iterative adjustments before a final suitable tension is achieved in each cable. See also, U.S. Patent Nos. 4,165,552; 4,437,201; 4,498,213; and 5,097,564, all of which are expressly incorporated herein in their entireties. Accordingly, there exists a need in the art for a cable drive system for a soot blower which employs a single drive cable, and wherein the length of the soot blower housing may be relatively reduced. SUMMARY OF THE INVENTION

The present invention is directed toward an improved cable drive system for a soot blower wherein a single drive cable is employed and wherein the overall length of the soot blower housing may be advantageously reduced, as compared to the prior art cable drive systems. In accordance with the present invention, a soot blower cable drive system includes a drive cable, a drive pulley, a driven pulley, and a pair of front idler pulleys. The driven pulley includes upper and lower grooves for receipt of the drive cable. The front idler pulleys are incorporated into a front tensioning assembly, which is adjacent a front cable mounting assembly. In further accordance with the present invention, the drive cable extends from a rear mounting and tensioning assembly, around the upper groove in the driven pulley, around the drive pulley, forwardly and around the front idler pulleys, rearwardly and around the lower groove in the driven pulley, and then forwardly to the front mounting assembly. In accordance with a second embodiment of the present invention, a rear idler pulley is provided intermediate the driven pulley and the drive pulley, and the drive pulley has upper and lower grooves for receipt of the drive cable. The drive cable extends from the rear mounting and tensioning assembly, around the upper groove in the driven pulley, around the upper groove in the drive pulley, forwardly and around the rear idler pulley and back around the lower groove in the drive pulley, forwardly and around the front idler pulleys, rearwardly and around the lower groove in the driven pulley, and then forwardly to the front mounting assembly. In further accordance with the second embodiment of the present invention, provision of the rear idler pulley and a pair of cable receiving grooves in the drive pulley increases frictional engagement between the drive pulley and the drive cable, thereby reducing the possibility of slippage, and resulting wear, of the drive cable and drive pulley. Moreover, the cable tension required to provide the necessary friction between the drive cable and the drive pulley is reduced. In accordance with the present invention, provision of a pair of front idler pulleys, incorporated into a front tensioning assembly, reduces the overall length of the soot blower assembly, as compared to prior art having a single large idler pulley. Reduction of soot blower housing lengths is desirable in many installations for space is often limited.

BRIEF DESCRIPTION OF THE DRAWINGS These and further features of the present invention will be apparent with reference to the following description and drawings, wherein: FIG. la is a top plan view of a soot blower; FIG. lb is a cross sectional view of the soot blower as seen along line A-A of FIG. la; FIG. lc is an enlarged top plan view of a forward portion of the soot blower; FIG. Id is a cross sectional view of the soot blower as seen along line B-B of FIG. lc; FIG. le is an enlarged view of a portion of FIG. Id; FIGS. 2a-2b schematically illustrate a cable drive system according to the present invention; FIG. 3a is a top plan view of an idler pulley according to the present invention; FIG. 3b is a cross sectional view of the pulley as seen along line 3b-3b of FIG. 3a; FIG. 4a is a front elevational view of a pulley shaft; FIG. 4b is a cross sectional view of the pulley shaft as seen along line 4b-4b of FIG. 4a; FIG. 5a is a perspective view of a pulley housing according to the present invention; FIG. 5b is a top plan view of the pulley housing; FIG. 5c is a cross sectional view of the pulley housing as seen along line 5c-5c of FIG. 5b. FIGS. 6a-6b schematically illustrate a second preferred embodiment of the cable drive system according to the present invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawing figures, a soot blower 10 according to the present invention is illustrated. The soot blower 10 includes a housing 12 in which a traveling carriage 14 is movably mounted and to which a drive motor 16 is attached. The drive motor 16 rotatably drives a drive pulley 18 via a gear box 20. The drive pulley 18 is fixedly located at a rearward end of the housing 12. The drive pulley 18 has a drive cable 22 wrapped therearound, as will be described more fully hereafter. A rear cable tensioning assembly 24 is secured to a rear portion of the housing top wall. The rear cable tensioning assembly 24 includes an upstanding U-shaped mounting flange having an opening through which a threaded rod 26 extends. The traveling carriage 14 includes a driven pulley 28 that receives the drive cable 22. The driven pulley 28 has an upper groove 28a and a lower groove 28b that receive the drive cable 22, as will be discussed more fully hereafter. The traveling carriage 14 moves between a rearward end of the soot blower housing 12 and a forward end of the housing, to extend a lance tube 30 into, and retract the lance tube 30 from, a boiler. For more information regarding the travelling carriage and associated mechanism for converting rotary motion at the driven wheel into rotary motion at the lance tube, reference should be made to commonly owned U.S. Patent application Serial No. 08/761,239, filed December 6, 1996, the disclosure of which is expressly incorporated herein in its entirety. A front cable tensioning assembly 32 is located at a forward end of the housing, as illustrated. The front cable tensioning assembly 32 includes a pair of idler pulleys.34, and means to permit forward/rearward movement of the idler pulleys 34 to adjust the tension on the drive cable 22. A front cable tie off 36 is attached to a forward end of the housing, relatively behind the front cable tensioning assembly 32. The means to permit drive cable tension adjustment include, in addition to the idler pulleys 34, an idler pulley housing 38, a pair of idler pulley shafts 40, and a pair of spring assemblies 42. With reference to FIGS. 3a-3b, one of the idler pulleys 34 is shown. The idler pulley 34 has a central bore in which bearings 44 are disposed. The bearings 44 are provided to rotatably support the pulley 34 on the pulley shaft 40, which is received in the opening and surrounded by the bearings 44. The idler pulley 34 also defines a peripheral groove 46 in which the drive cable 22 is received. With reference to FIGS. 4a-4b, the pulley shaft 40 has a generally cylindrical body in which a lubricating passage 48 is formed to direct lubricating fluid to the pulley bearings 44. The ends of the shaft 40 include annular grooves 50 that permit the shaft 40 to be secured to the pulley housing 38, as will be discussed hereinafter. With reference to FIGS. 5a-5c, the pulley housing 38 has an elongated shape, including a central portion 52 defined by identical spaced-apart upper and lower walls 56 and a pair of end portions 54. Each of the walls 56 have a pair of openings 58 through which the ends of the pulley shaft 40 project. The ends of the shafts 40 are secured to the pulley housing 38 by annular spring clips (not shown) that snap into the annular grooves 50 and thereby prevent axial movement of the shafts 40 relative to the pulley housing 38. The pulley housing end portions 54 have holes 60 that are generally transverse or perpendicular to the openings 58 in the upper and lower walls 56. The end portions 54 extend through openings in the soot blower housing side walls. With reference to FIGS, la-le, the spring assemblies 42 include a compression spring 62, a pair of washers 64, and a threaded rod 66. The spring assemblies 42 are secured to the idler pulley housing 38 and are mounted generally between a pocket member 68, which receives the end portion 54 of the pulley housing 38, and a flange member 70. More specifically, each rod 66 extends through one of the holes 60 in the pulley housing end portion 54 and through an opening in the pocket member 68, and has a retaining nut(s) secured to an end thereof. The pair of washers 64 and the spring 62 are placed over the rod 66, and held in place by means of a retaining nut(s), as illustrated. The spring 62 serves to maintain the drive cable 22, which is mounted over or around the idler pulleys 34, at a desired tension by acting on the pulley housing 38. If more or less tension is desired, the amount the spring 62 is compressed is varied, as should be apparent to one skilled in the art. Providing a pair of idler pulleys 34 instead of one large pulley has a number of advantages. Firstly, the pair of pulleys 34 has a much smaller profile than a single large pulley. Therefore, the length of the soot blower housing can be reduced for a given desired soot blower lance tube travel or extension. Moreover, the pair of idler pulleys may be better balanced and may provide improved operating characteristics for the cable drive system, as compared to a single idler pulley design. Finally, the pair of pulleys 34 are mounted upon an adjustment device whereby the position of the pulleys 34, and the tension on the drive cable 22, may be readily adjusted. The drive cable 22 is mounted as follows: One end of the drive cable 22 is attached to the threaded tensioning rod 26 at the rear cable tensioning assembly 24. The cable extends rearward from the threaded tensioning rod 26 and over a horizontal axis rear tensioning pulley 72, and then forwardly and around a top groove 28a of the traveling carriage driven pulley 28. From the traveling carriage driven pulley 28, the cable extends rearwardly and around the drive pulley 18 and then forwardly and around the pair of front idler pulleys 34. Thereafter, the cable 22 extends rearwardly and around the bottom groove 28b of the traveling carriage driven pulley 28. From the driven pulley 28 the cable 22 extends forwardly and is attached to the front cable tie off 36. The tension on the cable 22 can be easily be adjusted by manipulation of the front cable tensioning assembly 32 and/or the rear cable tensioning assembly 24. With reference to FIGS. 6a-6b, a second preferred embodiment cable drive system according to the present invention is illustrated. The second preferred embodiment is identical to the first embodiment in a number of respects. As such, identical structural features are given the same reference numerals in FIGS. 6a-6b as were assigned in FIGS. 2a-2b, discussed hereinbefore. The second embodiment of the cable drive system is desirable is some situations wherein the single cable wrap taught in the first embodiment is less than optimal due to inability to develop the necessary friction between the cable and the drive pulley 18a. A lack of friction may cause the cable to slip, which results in improper movement of the travelling carriage and lance tube, and increases wearing of the drive cable 22a and the drive pulley 18a. Although increasing the tension on the drive cable should produce the necessary friction and eliminate slippage between the drive cable and the drive pulley, the second embodiment is presented as an alternative to tensioning and, possibly, over-tensioning of the drive cable. In the second embodiment, the drive pulley 18a has a pair of grooves 82a, 82b which receive individual loops or portions of the drive cable 22a. A rearward idler pulley 80 is mounted to the soot blower housing 12, and is disposed near the drive pulley 18a. The drive cable 22a extends rearwardly from the tensioning rod 26 at the rear cable tensioning assembly 24 and around the horizontal axis tensioning pulley 72, around the upper groove 28a of the driven pulley 28. From the upper groove of the driven pulley, the drive cable 22a extends rearwardly and around the upper groove 82a of the drive pulley 18a, forwardly and around the idler pulley 80, and then rearwardly and around the lower groove 82b of the drive pulley 18a. From the lower groove 82b of the drive pulley 18a, the cable 22a extends forwardly and around the front idler pulleys 34, and then rearwardly and around the lower groove 28b of the driven pulley, and thence to forwardly to the front cable tie off 36. Provision of the drive pulley 18a with a pair of cable-receiving grooves 82a, 82b permits the necessary frictional engagement between the drive pulley 18a and the drive cable 22a at reduced cable tension levels, as compared to the single groove drive pulley 18 taught in the first embodiment of the present invention. While the preferred embodiments of the present invention are shown and described herein, it is to be understood that the same is not so limited but shall cover and include any and all modifications thereof which fall within the purview of the invention as defined by the claims appended hereto.

Claims

WHAT IS CLAIMED IS:

1. A soot blower, comprising: a housing having a forward end and a rearward end; a travelling carriage mounted in said housing for reciprocal movement between an extended position and a retracted position, said travelling carriage including a driven pulley and a lance; a drive cable; a forward tensioning assembly associated with said drive cable and operable to adjust cable tension; a drive mechanism including a drive pulley, said drive pulley being disposed in said housing relatively rearward of said driven pulley; a rearward tensioning assembly associated with said drive cable and operable to adjust tension on cable tension; and, a pair of front idler pulleys, wherein said drive cable extends from a rear mounting member, around said driven pulley, around said drive pulley, around said front idler pulleys, and again around said driven pulley to a front mounting member.

2. A soot blower according to claim 1, wherein said pair of front idler pulleys are incorporated into said front tensioning assembly and are movable toward and away from a front of said housing to adjust tension on said drive cable.

3. A soot blower according to claim 2, further comprising a rear tensioning pulley, said rear tensioning pulley having a horizontal axis and being secured to said housing relatively rearward of said rearward tensioning assembly.

4. A soot blower according to claim 3, further comprising a front cable tie off, said front cable tie off having one end of said drive cable secured thereto and being disposed relatively rearward of said forward tensioning assembly.

5. A soot blower according to claim 1, wherein said driven pulley includes defines an upper peripheral groove and a lower peripheral groove, said upper and lower grooves receiving portions of said drive cable.

6. A soot blower, comprising: a housing having a forward end and a rearward end; a travelling carriage mounted in said housing for reciprocal movement between an extended position and a retracted position, said travelling carriage including a driven pulley and a lance; a drive cable; a forward tensioning assembly associated with said drive cable and operable to adjust cable tension; a drive mechanism including a drive pulley, said drive pulley being disposed in said housing relatively rearward of said driven pulley; a rearward tensioning assembly associated with said drive cable and operable to adjust tension on cable tension; a rear idler pulley secured to said housing relatively between said driven pulley and said drive pulley; and, a pair of front idler pulleys, wherein said drive cable extends from a rear mounting member, around said driven pulley, rearwardly and around said drive pulley, forwardly and around said rear idler pulley, rearwardly and around said drive pulley, forwardly and around said front idler pulleys, rearwardly and around said driven pulley, and then forwardly to a front mounting member.

7. A soot blower according to claim 6, wherein said pair of front idler pulleys are incorporated into said front tensioning assembly and are movable toward and away from a front of said housing to adjust tension on said drive cable.

8. A soot blower according to claim 7, further comprising a rear tensioning pulley, said rear tensioning pulley having a horizontal axis and being secured to said housing relatively rearward of said rearward tensioning assembly.

9. A soot blower according to claim 8, further comprising a front cable tie off, said front cable tie off having one end of said drive cable secured thereto and being disposed relatively rearward of said forward tensioning assembly.

10. A soot blower according to claim 6, wherein said driven pulley defines an upper peripheral groove and a lower peripheral groove, said upper and lower grooves receiving portions of said drive cable.

11. A soot blower according to claim 10, wherein said drive pulley defines an upper peripheral groove and a lower peripheral groove, said upper and lower grooves receiving portions of said drive cable.

12. A soot blower according to claim 11, wherein said pair of front idler pulleys are incorporated into said front tensioning assembly and are movable toward and away from a front of said housing to adjust tension on said drive cable.

13. A soot blower according to claim 12, further comprising a rear tensioning pulley, said rear tensioning pulley having a horizontal axis and being secured to said housing relatively rearward of said rearward tensioning assembly.

14. A soot blower according to claim 13, further comprising a front cable tie off, said front cable tie off having one end of said drive cable secured thereto and being disposed relatively rearward of said forward tensioning assembly.